Printing plate and process of making same



Jan. 13, 1931. R A, @LASER 1,789,138

PRINTING PLATE AND PROCESS OF MAKING SAME Filed July 25, 1928 gwmm Pudo/ph ZZ /zifer` 1lb' amine@ Patented Jan. 13, 1931 UNITED STATES RUDOLPH`A. GLASER, OF CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

PATENT OFFICE GARDNER ABBOTT, AS TRUSTEE l PRINTING PLATE AND PROCESS 0F MAKING SAME Application led July 25, 1328.. Serial No. 295,266.

f A part of the subject matter hereofis disclosed in lny copending application Serial No. 180,590.

This invention relates to printing plates and photomechanical processes of making them and aims generally to improve such plates and processes. Although the invention is particularly advantageous as applied to large size plates for odset or direct lithographieprinting and is applicable for pictorial color .work in any number of desired colors, it is to be understood that printing plates and processes embodying the invention are applicable to other types of printingiand reproduction.

The invention aims to secure the sharp detail and truthful representation of the colors and tones of the original copy when applied to one color ory multi-color printing, and to improve the brilliancy and tone values of the printed copies as compared with those made by existing commercial processes and plates; 'to shorten the time and to reduce the cost heretofore required4 to make a set of color printing plates; and to produce a durable printing surface that will give a large number of impressions Ibefore losing its sharp detail, and that may be readily restored for further printing by mechanical means.

Other objects and advantages of the invention will appear inconneetion with the following description of an illustrative plate and mode of making it intended f or use-in printing posters. y

For purposes of illustration, the invention will be described as applied to` an intaglioplanographie printing plate adapted for use in offset lithographie printing, although it is understood that the inventionv is applicable to printing by direct lithographie printing, photogravure,l rotogravure, rotary photo- `gravure and other processes.

The intaglio-planogra'phic type of plate referred to herein is characterized by having -the ink receiving surface defined by a greasy condition that inheres in the grain of the metal and neither flows nor spread-s, and that is so intimately connected to the metal as not to be removable therefrom by washing or scrubbing, as distinguished from plano- -graphic plates having the image aiixed to the surface of the plate by a transfer process or developed upon or in a coating applied to the surface of the plate.

In the drawings, Figs. 1,l 2 and 3 indicate diagrammatically the successive steps'taken in the development of the image and treatment of the plat-e to form a permanent print'- ing surface.

According to the illustrated form of the invention a suitable -sheet 10, as for instance, a metal plate of zinc, aluminum or other suit.- able metal or alloy,'is lightly grained on its printing sideto improve its affinity for Water but not suiiieiently to form a printing pattern,and is given a very thin coating 11 of light sensitive "material, suehas biehromated gelatine or albumen, which is dried by whirling or otherwise.

The coating 11 is exposed to light for a short interval to fix it, whereupon it is wetted and coated again preferably with sensitized albumen, the second coating 12 being spread uniformly thin throughout and dried by whirling or otherwise.

The coated plate is thenA ready to be exposed to aetinic light rays passed through a' transparent image and a sri-called lithographie screen in a suitable apparatus, as, for example, thatdescribed in Pifer Patent No. 1,347,824, dated July 27, 1920, for photographic apparatus, wherein the metal plate may be supported in the holdenin place of the sensitized transfer sheet therein described. If a screen produced negative, such asa halfitone negative forl example, beused for the transparent image, a lithographie screen is not necessary.. Other types of apparatus may be employed, as the invention contemplates projecting or photographing the image tothe coated plate by actinic light rays, in any suitable manner.

rlhe source of the light rays is preferably a carbon are lalnp so constructed that the positive carbon is disposed in axial alinement with the direction of the projected rays, and is caused to revolve constantly so as to maintain a crater at its pointwhich holds a small volume of incandescent gas or vaporized metals produced by the are..

The coated plate will be affected where struck by suitable light rays penetrating the coating as is indicated in Fig. 1, where the non-light-struck portions 13 and light-struck portions 1-1 are clearly indicated. The intensity and character of the light rays have an important' bearing on the speed of .the exposure and the character of the printing plate produced, and I have discovered that a rotating carbon lamp produces the most satisfactory results. lVhethcr this is due to peculiar properties of-the pro]ected ray or to increased intensity of the ray 1s not known to me.

Instead of first washing away the nonlight-struek portions of the coating aml developing the light-struck portions to form the printing image, has been the usual practice heretofore, the exposed Vplates are flowed with a developing and penetrating compositionA containing a Water repelling substance, preferably an asphaltum mixture containing a greasy ink if the plate is to be used in lithographie printing, which composition is spread evenly and allowed to dry. The particular ingredients and proportions of each in the composition may be determinedby experience to suit the nature of the plate, but should be sufficiently/fluid to flow readily. A composition suitable for the purpose is as follows:

' Ounces Lithographie transfer ink 5l Lavender oil .4 Asphaltum 12 lBenzol 12 Turpentine 6 To which may be added six ounces of benzine.

The effect of the asphaltum mixture on the light-struck portions 14 of the Coating 12 and the coating 11 is to sink through and change its character where`there are printing dots inthe image, leaving the non-lightstrnck portions 13 unaffected to form the water dots on the plate which do not take ink, as indicated in Fig. 2, wherey patches of asphaltum mixture 15 are deposited upon the metal except where the latter 1s protected by the non-light-struck portions 13. The asphaltum mixture adheres to the metal and penetrates or is embedded beneath or 1n its surface, forming a sunken image composed of dots when a lithographie grain screen or screen produced image is used. 'l`he c henncal action, if any, of the asphaltum mixture upon the. surface of the metal plate is not. clearly understaiodmt thisltime. but it seems to have an effect upon themetal, changing its character, giving it a selective affinity for lithographie ink, so as to fix the image therein, as it has been foundpossible to recover the printing image after it has apparently lbeen completely lost without resorting to rcexposure to the master-copy.

As soon as the plate is sufficiently dry atte'. flowing it. with the asphaltum mixture, it is developed in warm water with theaid of cotton, whereupon the light sensitive coatings 11V -and 12-are entirely washed away leaving the grayish slinken image formed by the asphaltum mixture, as shown in Fig. 3. The plate is then powdered with soapstone and cleaned with tannic acid and resin, or other suitable cleaning compositions, followingwhich it lnay be treated again with asphaltum mixed with benzol, or asphaltum varnish, to strengthen the image, and any touching up needed may he given to it -in any manner known in the lithographie art before. rolling it up to make it ready for the press in the usual way. Both lithographie and deep etched plates may be produced in this manner for offset and dry printing.

The effect of. the printing is lnuch like that produced from intaglio plates` that is. the

printed image is more brilliant than that produced by ordinary lithographie or planographic plates wherein the ink is carried on the surface produced by transferring'an ink image to the plate. because the printing image is printed into the plate with strong actinic rays of light, giving a sharp clean image which takes a thick body of ink for transfer to the print.

Printing plates made according to my invention are entirely suitable for multi-color Work, and faithfully reproduce all of the lfine tints and tone effects of the original copy. The process of making the plates is very rapid, requiring but a few hours for the completion of a set of plates for printing in five or six colors, and is comparatively inexpensive.

My improved printing plate is capable of producing high grade printing at exceedingly high speed, and'is capable of printing a large number of impressions without losing its Sharp detail. Furthermore, should the'printing image be slightly damaged or accidentally lost through negligence of unskilled Workmen, vit can be readily restored by coating with asphaltum mixture and treating as before described.

In the claims the terms lithographie light sensitive coating and lithographie light permeable coated surface include those light sensitive coatings used in lithographie and planographie printing which are disintegrated by the action of intense light or thereby rendered permeable to the. asphaltum .mixture or equivalent. developing ink. and although have referred specifically to thi.l use of sensitized gelatine or albumen as preferable in the illustrated form of t-he invention, other known lithographie sensitized coatirgs having the described properties may be used.

Changes in the process to suit 'unusual or special subjects, or for the convenience of individual'useis may be readily, inade by those skilled in the ait.

lVhat I claim as my invention is as follows:

1. The process of making lithographie 'printing plates which consists in photographing an image directly to the 4plate by the action of` high intensity actinie light rays upon a lithographie light permeable coated printing surface thereof to render portions thereof permeable to a developing composition, treating the coated plate with a greasy asplialtum developing composition to forni the printing image thereon', which permeates jthe surface of the plate, and then removing the remaining portions of the coating.

2. The process of making metal printing 'plates f'wliich consists in photographing an image directly to the plate by the action of high intensity aetiniclight rays upon a lithographic light permeable .coated printing lithographie coated printing surface thereofpermeable to such 'a light, impregnating the light-struck portions of the plate with an asphaltuni ink solution to form an ink-receiving image, washing away the light-struck portions of the coating, and cleaningtlie bare surface of the plate to form a surface capable of taking moisture and resisting ink.

4. The process of making lithographie printing plates which consists in projecting van innige bythe action of light upon a light permeable lithographie surface coating o f a grained printing plate capa-ble of being 1mpregnated by a developing ink, impregnating the light-struck portions of the surface with an asplialtum ink solution to form an ink-receiving image on the plate, washing away the surface coating and then cleaning thc bare surface of the plate notcovered by the asphaltum image to form a surface capablc of taking'moisture and resist-ing ink.

5. The process of making printing plates which consistsy in coating-the plate With'a lithographie light sensitive-solution normally impermeable by as-plialtum greasy ink but permeable to saidjink when affected by light of high intensity, photographing the image upon said coating by the action of light of `high intensity to penetrate the coating above i the printing surface, covering said coating with said ink to'fix the ink-receiving image directly upon and penetrating the plate, and

then washing away the coating and ink .eX- ept that constituting Vsaid ink-receiving image.

6. T he process of making intaglio-planographle printing plates which consists in proJecting an image directly to the plate by the action of actinic light rays of high intensity upon-a lithographie light permeable coating covering the printing surface thereof, transtixing the light-struck portions of the sensitized plate with a mixture containing bituminous material to form the printing image penetrating the plate and then reinovino' the remaining portions of the coating.

The process of making lithographie printing plates which consists in-projecting an image by the action of light upon a lithographic light sensitive coating on the grained y plate capable of being impregnated by an ink selective composition, and then changing the character of the surface of the plate in regions underlying the light-struck portions of the-plate by means of a solution capable of penetrating the light-struck portions of the `coating and sinking into the grain of the plate.

8. The proes of making printing plates which consists in coating the grained plate capable of being impregnated by a developing ink with a lithographie light sensitive material `normally impermeable by greasy ink but permeable to said ink when affected by light,- photographing the image upon said coating by the action of light rays to penetrate the coating above the'printing surface, covering said coating with said ink and then Washing away the coating and ink except in regions Where the ink has penetrated the plate.

9. The process of preparing metallic printl ing plates which consists in coating a metal plate grained to receive water, with a lithographic albuminous coating soluble in water, i

transferring an image to said coating by the action of light, penetrating the surface of the plate byA a greasy mixture through thc liglit-struck portions of the coating, and Washing away the coating to leave the waterreceiving surface of the plate surrounding the greasy image.

10. The process of making printing plates which consists in photograpliically projecting-'an image .directly upon a lithographie light permeable coated surface of. a printing plate. by the action of high intensity actinic light rays to render the light struck portions permeable to a developer, treating theentire coated surface of the plate with an ink selective developer capable of penetrating the metal plate to Idevelop the printing-image firmly ingrained in said plate, andthen removing the portions of coating and developer surrounding the image.

11. The `proce'ss'of making printing plates which consists in photographically projectin an image directly upon a lithographie lig t permeable coated surface of a printing plate by the action lof high intenslty actinic light rays to render portions thereof permeable to a. developer, treating the entire coated surface of the plate `with an asphaltum developer having'an affinity for greasy ink but repellant to water to develop the printing image firmly ingrained in said plate and then washing away with Water the p0rtions of' coating and developer surrounding the image.

12. An intaglio-planographic metal printing plate having a lithographie albuminous coating on one face thereof. portions of which are disintegrated by light, and an aspbaltum ink composition penetrating said albuininous coating where disintegrated and I sinking into and penetrating said metal plate printing image capable of receiving ing image having a selective affinity for ink,

said light-affected areas being of permanent character so that the prmtmg image, 1f removed, may be rebullt according to the orig- .inal image by retreatment with the asphaltumnmaterial.

15. An intaglio-planographic metal printing plate having a finely grained surface and areas permanently affected byligbt corresponding to a photographic image, said light affected areas being impregnated by barden'ed-material of permanent character having a selective affinity for ink.

16. Aphotographie printing plate penetrable by anink-select-ive composition, and having a grained surface to take water and light-'struck areas of permanent character corresponding to a photographic image, said areas being covered by hardened greasy material penetrating the plate.

17. A photographic printing plate pencfrable by an asphaltum composition, and having a grained surface to take water and light-struck areas of permanent character corresponding to a photographic image,said arcas being covered by hardened asphaltum base material penetrating the plate.

18. A photographic intaglio-planographic metal print-ing plate having permanent lightstruck reas corresponding to a photographic image, said arees being impregnated by inkreceiving portions of hardened asphaltum base material.

19. A photographic intaglio-planographie metal printing plate having permanent light-struck areas corresponding to a photographic image, said areas being impregnated.

by ink-receiving portions olfV hardened asphaltum base material sunken therein.

20. A metal intaglio-planographie printing plate having ay finely grained surface capable of receiving water and light-'struck areas corresponding to a photographic image, said plate, where affected by light, being covered by hardened non-metallic ink-receiving portions impregnated in said metal plate and constituting a printing image sunken therein.

21. A metal intaglio-planographic printing plate having a finely grained surface capable of receiving Water and light-struck areas corresponding -to a photographic image, said plate, Where affected by light, being covered by hardened bituminous ink-receiving portions impregnated in said'metal plate and constituting a printing image sunken therein.

In testimony whereof, I have signed my name to this specification.

RUDOLPH A. GLASER. 

